I had oil change at dealership and a few weeks later oil light came on and it started to ding.it would go off for a while then start up again.I took the car in too be checked and it was three quarts low. The exhaust is black and smells of oil. I and taking it back in a week later as the engine light is on. It has 52000 miles.
Not what you want to hear, but you really need to learn how to check your oil level at least once a week . Also it is recommended to check it after an oil change before leaving the place that did it. If that is not possible at least check after you get home.
Not much can be said until you have the dealer look at it but taking it back and them finding it low on oil may just take them off the hook.